This invention generally relates to the field of product casting and more particularly to a novel photopolymeric molding/impression pattern and method of forming the same.
The art of casting involves the introduction of a material in an initial liquid state, e.g. molten metal, into a cavity or mold where, upon solidification, it becomes an object whose shape is determined by the configuration of the cavity or mold. There are two broad categories of casting processes, i.e. ingot casting and casting-to-shape. The latter process involves pouring the liquid into a cavity which has been configured to provide the final useful shape of the product. Casting-to-shape is generally classified according to the molding process and material or method of feeding the mold. Within this process are four basic types including sand, permanent-mold, die and centrifugal.
Sand casting provides the traditional method of casting-to-shape and is of particular interest as it produces the largest volume of casted-to-shape products. The basic process utilizes a mixture of sand grains, clay and other materials which is compacted around a pattern. Upon removal of the pattern, a cavity having a configuration corresponding to the pattern's configuration is impressed/presented within the surrounding mixture which corresponds to the desired shape of the product. Molten metal is then poured into the cavity and upon cooling assumes the shape thereof. The process can be repeated to present a plurality of casted-to-shape products having the same configuration.
An important step in sand casting is the preparation of the pattern. Patterns may be made from any material which will hold its shape during compaction of the surrounding sand mixture. A variety of materials can be used in pattern construction inclusive of wood, metal, aluminum alloy, cast iron, brass, plaster of paris etc. The pattern material used depends on the type and design intricacies of the finished casted product.
The use of a brass pattern is preferred in the casting of products which call for design intricacies thereon such as a textured or otherwise designed background relatively offset from the primary design of the finished product. Previously, such design intricacies had to be hand-engraved on the brass pattern which requires expensive skilled labor. This engraving expense increases the pattern cost which is necessarily reflected in the cost of the finished product. Accordingly, it is desirable to find an efficient cost-effective method of making a cost-effective pattern having design intricacies therein which are transferred to the finished product in a manner comparative to that of hand-engraved patterns.
In response thereto, I have devised a method of making an impression/casting pattern of a photopolymeric material which transfers design intricacies to the finished product without the utilization of an expensive hand-engraved brass pattern or the like. I utilize the sequential passage of ultraviolet light waves through designs on first and second image negatives which are sequentially located on opposed sides of a light-sensitive photopolymeric resin. The ultraviolet waves sensitize/harden the resin in configurations corresponding to the design images on the respective negatives. My method forms a pattern having a primary design thereon corresponding to the design image on one negative and a background design relatively offset from the primary design and having design intricacies in relief thereon corrresponding to the design image of the other negative. Upon mounting the finished pattern to a mounting plate or an impression blank corresponding to the overall product shape or a portion thereof, the rigidified pattern is suitable for use as an impression pattern in a casting-to-shape process for transfer of the primary and secondary designs to the finished product. Heretofore, such design intricacies were available only by utilizing a metal pattern having the design intricacies engraved thereon. Although I shall describe my novel pattern in relation to a belt buckle, it is understood that the resulting finished product and employed process to arrive at said finished product are not considered limitations on my invention.
It is therefore a general object of this invention to provide a new method for making an impression pattern having qualities comparable to a hand-engraved impression pattern.
Another general object of this invention is to provide a new method for making an impression pattern for use in a casting process or the like.
Still another object of this invention is to provide a novel impression pattern and method of making the same, as aforesaid, utilizing a photopolymeric resin as the pattern material.
Another particular object of this invention is to provide an impression pattern and method of making the same, as aforesaid, which utilizes first and second image negatives sequentially placed on opposed sides of said resin for sequential passage of ultraviolet light waves therethrough in a manner to shape the resin according to the design images of said negatives.
Another particular object of this invention is to provide an impression pattern and method of making the same, as aforesaid, wherein said pattern presents primary and secondary images in relief from a common background.
A still more particular object of this invention is to provide a pattern, as aforesaid, in which said secondary relief image is provided by the design image on one of said negatives with the primary relief image provided by the design image on the other said negatives.
Still a more particular object of the invention is to provide an impression pattern and method of making the same, as aforesaid, having design intricacies on said background in relative relief thereto.
Another object of this invention is to provide an impression pattern and method of making the same, as aforesaid, which is easily combined with a mounting plate or impression blank to present a composite impression pattern.
Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, a preferred embodiment of this invention.